1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer, a digital copier, and a facsimile. More particularly, the present invention relates to a process cartridge, an image forming apparatus incorporating the cartridge, and a method for mounting and dismounting the process cartridge in and from an image forming apparatus body.
2. Description of the Related Art
Generally, an electrophotographic image forming apparatus such as a laser printer, a digital copier, and a facsimile comprises a process cartridge including a developing unit or integrating a photosensitive body unit and a developing unit into a single module. A photosensitive body of the photosensitive body unit is exposed to a laser to form an electrostatic latent image thereon. The developing unit supplies developer to the photosensitive body to form a developer image corresponding to the electrostatic latent image.
Generally, the process cartridge is detachably mounted in an image forming apparatus body to easily repair or replace all parts of the cartridge.
FIGS. 1, 2A and 2B are views of a general process cartridge 1 in which the photosensitive body unit and the developing unit are integrated into a single module.
The process cartridge 1 comprises a photosensitive body casing 2 and a developing casing 8.
In the photosensitive body casing 2, a photosensitive body unit is formed which comprises a photosensitive body 7 having a drumlike configuration, a charging roller 8 for charging a surface of the photosensitive body 7, and a cleaning member (not shown) such as a cleaning roller and a cleaning blade for cleaning the photosensitive body 7.
On an upper portion of the photosensitive body casing 2, a knob 6 is provided to carry and move the process cartridge 1.
A first and a second side members 14a, 14b are provided on the opposite end portions of the photosensitive body casing 2.
On the first and the second side members 14a, 14b are formed a first and a second guide protrusions 24 (only the first guide protrusion is shown) protruding to the outside to be coaxially aligned with an axis of the photosensitive body 7. A third and a fourth guide protrusions 25 (only the third protrusion is shown) protrude outwardly from the side members a certain distance from the first and the second guide protrusions 24.
As the process cartridge 1 is mounted in the image forming apparatus body, the first and the second guide protrusions 24 are guided along a first and a second guide recess 20a (only the first guide recess is shown) of a first and a second guide member 20 so as to be received in a receiving recess 20b of the first and the second guide recesses 20a. The first and the second guide protrusions 24 each are received in the receiving recess 20b so as to position the process cartridge 1 in a mounting position.
As the process cartridge 1 is mounted in the image forming apparatus body 1, the third and the fourth guide protrusions 25 are received in the first and the second guide recesses 20a. As the process cartridge 1 is mounted and dismounted in or from the image forming apparatus body, the third and the fourth guide protrusions 25 guide the movement of the process cartridge 1 and operate as a hinge point supporting the rotation of the process cartridge 1 in the first and the second guide recesses 20a. 
Accordingly, as the process cartridge 1 is mounted in the image forming apparatus and then, pulled or pushed in first and second directions P1, P2 by the knob 6, the process cartridge 1 is minutely rotated in the direction of arrow a, b based on the third and the fourth guide protrusions 25 as a hinge point. As a result, the first and the second guide protrusions 24 are received in the receiving recess 20b or separated from the receiving recess 20b of the first and the second guide recesses 20a. 
The developing casing 8 may be formed integrally with or detachably from the photosensitive body casing 2.
The developing casing 8 comprises a developing roller 10 contacting the photosensitive body 7 with a certain gap, a supply roller (not shown) supplying the developing roller 10 with developer, and a developer regulating blade (not shown) contacting the developing roller 10 to regulate the thickness of the developing layer.
The process of mounting and dismounting the process cartridge 1 in or from the image forming apparatus body for replacing or repairing the process cartridge 1 will be explained below.
To dismount the process cartridge 1 from the image forming apparatus body, the image forming apparatus body cover (not shown) is opened and the process cartridge 1 is pulled in the first direction P1 by the knob 6.
As a result, the process cartridge 1 rotated in the direction of arrow b using the third and the fourth guide protrusions 25 as a hinge point, as shown in FIG. 2B so that the first and the second guide protrusions 24 are moved upwardly and separated from the receiving recess 20b of the first and the second guide recesses 20a. 
Then, as the process cartridge 1 is pulled further in the first direction P1 by the knob 6, the four guide protrusions 24, 25 slide along the first and the second guide recesses 20a and are separated from the first and the second guide recesses 20a. 
Then, the process cartridge 1 is lifted upwardly and pulled out through the process cartridge body cover to the outside.
After the process cartridge 1 is pulled out of the image forming apparatus body to the outside, the process cartridge 1 is disassembled to repair problematic parts thereof or replaced with new one, if necessary.
After completing the repairing or replacing, the repaired or replaced process cartridge 1 is put through the image forming apparatus body cover into the image forming apparatus body to be mounted therein.
After fitting the first and the second guide protrusions 24 in the first and the second guide recesses 20a, the process cartridge 1 is pushed in the second direction P2 by the knob 6.
As the process cartridge 1 is nearly mounted in the image forming apparatus body, the third and the fourth guide protrusions 25 fit in the first and the second guide recesses 20a and then, the process cartridge 1 is pushed further in the second direction P2 by the knob 6. Therefore, the first and the second guide protrusions 24 contact with an end portion wall 20c of the first and the second guide recesses 20a as shown in FIG. 2B.
The process cartridge 1 is minutely rotated in the direction of arrow a using the third and the fourth guide protrusions 25 as a hinge point by inertial force and its own weight. Therefore, the first and the second guide protrusions 24 are inserted and received in the receiving recess 20b of the first and the second guide recesses 20a, as shown in FIG. 2A. Additionally, a photosensitive body gear 7a of one end portion of the photosensitive body 7 is meshed with a driving gear 21, transmitting a driving force of a driving motor, of a main gear train of the image forming apparatus body.
However, as the conventional process cartridge 1 with the above structure is mounted in the image forming apparatus body, the four guide protrusions 24, 25 of the first and the second side members 14a, 14b should be simultaneously inserted into the first and the second guide recesses 20a of the first and the second guide members 20. Accordingly, careful operations are required to accurately insert the four guide protrusions 24, 25 into the first and the second guide recesses 20a when the first and the second guide protrusions 24 are inserted in the first and the second guide recesses 20a and when the third and the fourth guide protrusions 25 are inserted into the first and the second guide recesses 20a after the first and the second guide protrusions 24 are inserted in the first and the second guide recesses 20a. Additionally, in order to completely fit the first and the second guide protrusions 24 in the receiving recess 20b of the first and the second guide recesses 20a, the process cartridge 1 should be continuously pushed in the second direction P2 by the knob 6 so as not to be freely moved.
Further, as the conventional process cartridge 1 is dismounted from the image forming apparatus body, the first through the fourth guide protrusions 24, 25 should be completely separated from the first and the second guide recesses 20a of the first and the second guide members 20 to pull the process cartridge 1 out of the image forming apparatus body 1 to the outside. Accordingly, as the process cartridge 1 is dismounted and mounted in or from the image forming apparatus body, the time required to remove the process cartridge 1 from the image forming apparatus body is delayed by the length of the first and the second guide recesses 20a. Additionally, if the process cartridge 1 is pulled out by force, the first and the second guide protrusions 24 and/or the third and the fourth guide protrusions 25 may be damaged.